UV radiators to provide radiation within the UV spectrum include phosphors or similar light emitting substances having maximum radiation output in the UV range, and particularly in the A range of UV and in the long wave B range. These lamps generate "black light" and some blue light. The visible light output of the lamps does not permit observation of tanning of human skin, for example of a patient.
It has previously been proposed--see German Patent 31 21 689, Wolff--to provide a therapeutic UV radiation lamp which, besides providing UV radiation in the A range also has in addition thereto a radiation emission within the orange-red range. The orange-red emitted spectrum is intended to cancel the effect of the black-blueish light of the UV radiation, so that a balanced light output is obtained which is supposed to be "normal". The orange-red light, however, results in an over-evaluation of the red portions of the particular color composition. Since the color of the skin has many reddish components, the appearance of the skin of a patient will be pink, with a disagreeable hue. It is not possible to observe differential tanning or coloring effects of the human skin, and thus checking tanning effects of the UV radiation is not possible under light emitted by lamps of this type.